What are the usage methods of a multimeter?
(1) Before using a multimeter, "mechanical zero adjustment" should be carried out. That is, when there is no measured electrical quantity, the pointer of the multimeter should be set at the position of zero voltage or zero current.
(2) During the use of a multimeter, one should not touch the metal part of the test leads by hand. On the one hand, this can ensure the accuracy of the measurement, and on the other hand, it can also ensure personal safety.
(3) When measuring a certain electrical quantity, the gear should not be shifted while measuring, especially when measuring high voltage or large current. Otherwise, the multimeter may be damaged. If it is necessary to shift the gear, the test leads should be disconnected first, and then the measurement should be carried out after shifting the gear.
(4) When using a multimeter, it must be placed horizontally to avoid errors. At the same time, attention should also be paid to avoiding the influence of the external magnetic field on the multimeter.
(5) After using the multimeter, the changeover switch should be set to the maximum range of the AC voltage. If it is not used for a long time, the battery inside the multimeter should also be taken out to prevent the battery from corroding other components in the meter.
When using an analog multimeter, one end of the two test leads should be inserted into the measurement terminal according to the requirement that the red lead is connected to the positive (+) and the black lead is connected to the negative (-). Then, it is necessary to confirm whether the pointer is at the "0" position. The pointer should be aligned with the end line on the left side of the dial. If it is inconsistent, zero adjustment should be carried out. Before measuring current and voltage, the range of the current and voltage to be measured should be estimated first. Set it to a larger gear first, and then adjust it to an appropriate gear to avoid burning out the multimeter due to excessive current.
When making a measurement, the influence of the internal resistance of the multimeter should be considered. For example, in order to measure the voltage, the test leads should be connected to the measured circuit. At this time, current also flows through the resistors inside the multimeter, which has a certain influence on the measured value. When measuring the voltage at the same point, if different gears are used, the internal resistance of the multimeter is different, and the degree of influence is also different.
When measuring a transistor electronic circuit, it is better to select an internal resistance of 20kΩ/V in the DC gear. This value is usually marked on the dial of the multimeter. In addition, for transistor circuits, it is often necessary to measure low-value voltages, such as 0.1V. At this time, the selected multimeter should have a measurement range of the 1V gear.
